The invention relates to a process and an arrangement for the removal of an embedding body made of a lower-melting material from an embedded higher-melting metal component or ceramic component.
It is known that embedding bodies of this type consisting of low-melting metal alloys or thermoplastics are cast around metal components or ceramic components of complicated shapes in order to embed these partially so that the embedded part can be chucked or fixed in machines while the unembedded part can be machined.
A known process for the removal of these embedding bodies from the embedded component is the melting-off of the embedding body in hot oil. This process has the disadvantages of the oil removal, of the necessary suction-removal of the oil vapors, of the long melting-off period, of the washing-off of the oil residues from the component, of the removal of oil residues, for example, from capillary bores in the component, of the removal of the washing-off medium and of the vapors of the washing-off medium, and the related environmental stress.
Another process consists of splitting the embedding body in a press by means of two separating bars. This process has the disadvantage that high uncontrollable pressures are exercised on the embedded component so that there is a high risk of rejections, and compact residues of the embedding material must be removed subsequently at certain points which again requires oil baths.
It is an object of the invention to provide a process and an arrangement of this type which ensures a low-residue removal of the embedding body which does not stress or deform the embedded component while the risk of rejections is reduced at the same time and the means used in the process are less stressful to the environment.
This object is achieved by a process in which the following steps are carried out:
a. placing a groove in the embedding body along the molding-in base of the embedded component; an
b. removing of the halves of the embedding body from the embedded component by widening the groove along the molding-in base.
This process overcomes the disadvantages of the previous process and saves considerable waste removal costs since no oil is used. In addition, the costs with respect to rejections are reduced since the embedding body is removed from the embedded component under the effect of minimal force after the providing of a groove, for example, by milling, sawing or grinding.
By means of a preferable melting-out of the groove, even advancing and cutting forces as well as abrasion marks of a possible cutting-in of the groove are advantageously avoided.
The melting-out has the additional advantage that arbitrary and also bent or curved groove cross-sections can be made in one operation because only the shape of the melting-out tool must be adapted to the cross-section of the groove.
A preferred embodiment of the process provides a melting-out at temperatures of between 50.degree. and 350.degree. C., preferably between 130.degree. and 180.degree. C. The large temperature range has the advantage that also thermoplastics may be used as the embedding material. In a narrower range, low-melting metals can be used as the embedding material, such as the metal alloy tin/bismuth with 30 to 70 percent in weight of bismuth.
The difference between the melting temperature of the embedding material and the melting temperature of the embedded component should be at least 150.degree. C. so that a possible local overheating of the component is avoided.
The embedding and removal is preferably used for components made of a nickel, cobalt or titanium base alloy from which guide blades or moving blades of axial-flow turbines and axial-flow compressors are made. In this case, the blade base and the blade tip can be machined while the finished blade with its capillary bores is chucked in in the embedded area.
The removal of the halves of the embedding body created by the provided groove from the embedded component may preferably take place by a pulling-apart, turning-apart, pushing-apart, pressing-apart or blowing-apart. This has the advantage that the halves of the embedding body are removed from the component without any large formation of residues. The finishing of the component is therefore minimized.
As far as the arrangement for carrying out the process is concerned, the object is achieved in that the arrangement has at least one heatable element which, in its dimensions, corresponds to the cross-section of the groove to be provided, and is arranged so that it can be moved in at least one direction in space and be rotated around at least one direction in space, and has a receiving device for the embedding body.
This arrangement has the advantage that it does not apply the groove in a cutting but in a thermal manner and thus has an extremely gentle effect on the embedded component so that damage to the component is largely avoided In addition, it does not require any fast-rotating tools so that it has a long service life and can be produced at low manufacturing costs.
As the melting-out tool, the arrangement has a heatable element which advantageously can be adapted to any desirable groove cross-section.
A preferred development of the heatable element provides that it is elastically mounted so that, during the melting-out, the tip of the heatable element can follow the contour of the embedded component without the requirement of any adjustment. This self-adjustment permits a complete dividing of the embedded body in two halves along the molding-in base so that these halves fall apart without an expenditure of force, for example, by being blown by a jet of compressed air.
If the component is embedded such that it projects out of the embedding body on two opposite sides, the arrangement preferably has two heatable elements in the form of two hot rods which simultaneously melt out a groove on the front edge and the rear edge of the component so that the melting-out operation is shortened and the productivity of the arrangement is increased.
Another preferred development of the arrangement has a blade-shaped heatable element the blade of which completely fills in the required groove along the front edge or rear edge of a correspondingly shaped embedded component in the embedding body with the exception of a melting gap. This melting gap is created automatically by the flowing-off of the melted-off embedding body material along the wall of the groove. This preferred development of the invention has the advantage that the melting-out operation is shortened further.
A further reduction of the melting-out time is achieved by means of an arrangement which preferably has two blade-shaped heatable elements which simultaneously fill in the whole groove on the front and rear edge of an embedded component, the arrangement making it possible that the groove is not melted out all the way to the component. Although this requires a higher expenditure of force during the removal of the embedding-body halves, it has the advantage that during the melting-out of the groove no melted material can penetrate into capillary bores or slots of the component.
In a preferred development, the heatable elements are arranged such that a groove is created which is vertical or which extends up to a slope of 60.degree. with respect to the vertical line. An arrangement of this type ensures the discharge of the molted-open embedding material into a drip pan without any additional auxiliary measures, such as the turning of the embedding body for the throwing-out or flowing-off of the melted mass.
The arrangement is preferably controlled digitally so that it can be used advantageously in mass production.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.